Method of preventing ice formation in a jet engine

ABSTRACT

METHOD OF OPERATING A JET ENGINE ON A HYDROCARBON TYPE JET FUEL CONTAINING A POLYETHOXYLATED PROPYLENE DIAMINE TO PREVENT FORMATION OF ICE CRYSTALS IN THE FUEL SYSTEM.

United States Patent T 3,574,577 METHOD OF PREVENTING ICE FORMATION IN A JET ENGINE Jerzy J. Bialy, Lagrangeville, and George W. Eckert, Wappingers Falls, N.Y., assignors to Texaco Inc., New York, N.Y.

No Drawing. Continuation-impart of application Ser. No. 394,038, Sept. 2, 1964. This application May 22, 1968, Ser. No. 731,331

Int. Cl. Cl1/22 U.S. Cl. 44-72 4 Claims ABSTRACT OF THE DISCLOSURE Method of operating a jet engine on a hydrocarbon type jet fuel containing a polyethoxylated propylene diamine to prevent formation of ice crystals in the fuel system.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of copending application Ser. No. 394,038, filed Sept. 2, 1964, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a novel fuel composition. More particularly, the invention relates to turbine or jet fuels having outstanding anti-icing properties. This improvement is based on the effect of an anti-icing additive consisting of a polyethoxylated propylene diamine.

Reliability of the fuel supply under extremely severe operating conditions is a matter of paramount importance in the operation of turbine or jet engine aircraft. It is also essential that the fuel supply be absolutely free of any suspended solid particles in order not to block or impair the operation of the fuel atomizer and other fine components in the jet engine. The provision of uncontaminated fuel free of solid particles to the engine is assured by passing the fuel through exceedingly fine filters in order to screen out any contained solid particles.

The prior art contains numerous references to the use of de-icing additives in gasoline-type motor fuels to prevent carburetor icing. We have found that the icing prob lems encountered in the operation of jet'engines are not analogous to those encountered in gasoline engine operation and that additives which are effective in gasoline are not necessarily effective in jet fuels. Although many materials are known in the prior art to be anti-ice formation additives in motor fuels of the gasoline type, in spite of the large amount of research which has been conducted by the petroleum industry on jet fuels there are relatively few materials which have been discovered to date which are effective in preventing ice formations in jet fuels. As an example, N-alkyl substituted alkylene diamine are effective anti-icing additives when used in gasoline type fuels in automotive engines but the same materials have been found to be ineffective anti-icing materials when used in jet fuels. As a matter of fact, there appears to be no correlation whatsoever between the effectiveness of various anti-icing materials in these two types of fuels.

3,574,577 Patented Apr. 13, 1971 SUMMARY OF THE INVENTION A jet fuel composition has now been discovered which inhibits or prevents the formation of ice from the water contained therein even under extremely low temperatures. This is achieved by the addition of very small amounts of an additive composition which imparts exceptionally good anti-icing properties to jet fuel compositions.

In accordance with this invention, there is provided a jet fuel composition containing 0.02 to 0.35 weight per cent of a polyethoxylated propylene diamine. Polyethoxylated propylene diamines are represented by the formula:

in which R represents an alkyl radical having from 10 to 30 carbon atoms, and in which subscripts x, y and z represent moles of ethylene oxide.

The alkyl radical can be either saturated or unsaturated and either straight or branched chain in structure, and for example, may be saturated alkyl radicals such as lauryl, behenic, etc.; unsaturated alkyl radicals such as oleyl, ricinolyl, etc.; or mixtures such as may be derived from a natural fatty oil such, for example as from coconut oil fatty acids, soya bean oil fatty acids, tallow oil fatty acids, etc.

The total moles of ethylene oxide, represented by the sum of subscripts x, y and z in the formula may vary from about two to ten moles and preferably two to six.

A preferred material for the practice of this invention is the commercial product Ethoduomeen T/l3 manufactured by Armour and Company in which R is derived from tallow oil fatty acids and which contains three moles of ethylene oxide (the sum of subscripts x, y and z).

The anti-icing additive of this invention is employed in turbine or jet engine fuel compositions. The fuels are made up of straight run or cracked hydrocarbon components in the gasoline and kerosene boiling ranges, i.e., boiling from about 100 to about 600 F. Commercial IP-4 type jet fuel, which consists of about percent gasoline and 35 percent middle distillate, is typical of the fuels improved by the anti-icing additive of the invention.

The jet fuel of the invention is conveniently prepared by mixing the base fuel with the polyethoxylated propylene diamine. As noted above, the jet fuel will generally contain from about 0.02 to 0.35 weight percent of the additive. The preferred range of proportion for the additive, however, are from about 0.05 to 0.20 weight percent.

An important feature of this invention is that the outstanding anti-icing properties imparted to the fuel are obtained with relatively small amounts of the additive. whereas heretofore, jet fuel anti-icing additives have been proposed in amounts of 0.5 to 1 percent or more, the present additive gives the desired properties with a very small amount of additive. For most purposes, effective anti-icing is obtained at about 0.10 weight percent of the :additive.

DESCRIPTION OF PREFERRED EMBODIMENT The performance of a jet fuel under actual operating conditions can be determined quite accurately on the basis of laboratory tests. The pumpability temperature test has been used with a considerable degree of success to determine the low temperature pumpability characteristics of a fuel. The results are reported as pumpability temperature. Pumpability temperature is the temperature at which the flow rate of the fuel can no longer be maintained and/ or substantial pressure drop develops as the result of accumulated ice crystals on a screen under controlled test conditions. In more detail, this pumpability or icing test as it is sometimes called, involves circulating the fuel through a fine metal screen filter in a closed system while gradually reducing the temperature of the fuel. Sensitive temperature and pressure devices placed on the inlet and outlet sides of the filter indicated the temperature at which a substantial pressure drop is brought about by the formation of ice in the fuel. For a detailed description of the test apparatus reference may be made to US. Pat. 3,167,411 which issued to us on Jan. 26, 1965.

The jet fuel employed for testing the additive of the invention had the inspection tests listed in Table I:

TABLE I Fuel inspection tests Gravity, API 52.8 Freezing point Below 76 Luminometer number, F. 62.8 Hyrocarbon group analysis FIA:

Saturates 89 Aromatics 10 Olefins 1 RVP c 2.3 ASTM distillation:

IBP 135 173 188 20% 212 30% 237 40% 263 50% 292 60% 321 70% 348 80% 398 90% 457 95% 485 EP 509 Recovered 98.5 Loss 1.1 Residue 0.4

The pumpability temperature for a water-saturated JP-4 fuel is usually between +5 and l5 F. With 2 ml. of free water per gallon of fuel, the pumpability temperature is generally in the range of +10 to +20 F.

Examples A JP-4 type of jet fuel having the inspection tests shown in Table I was tested for its pumpability temperatures under conditions of water saturation and with two ml. of excess water per gallon of fuel. The fuel was then tested with the addition of a minor amount, 0.1%

TABLE II Additive None 1 A B 0 Amount, wt. percent 0 0. 1 0. 1 0. 1

Pumpability temp., F., fuel sat. with water 8 76 76 76 Fuel plus 2 ml. water/gaL, "F 7 6 76 23 1 Base fuel.

From Table II it will be seen that additives A and B are equally effective in lowering the pumpability temperature of jet fuel when used in the concentrations shown. Where the pumpability temperature is shown as being 76 F., this is the lowest temperature required by the test. A value of 76 F. indicates that the pumpability temperature is at least this low and might be below this temperature.

In addition to their effectiveness as anti-icing additives in jet fuels as indicated by the pumpability temperature measurements reported in Table II, jet fuel containing additives A and B in the concentrations shown does not attack copper, cadmium or aluminum when in contact with these metals for two weeks at 140 F.

Additive C is a propylene diamine containing one alkyl radical derived from tallow oil fatty acids and which is manufactured by Armour and Company under the tradename Duomeen T and sold commercially as anti-icing additive for use in gasoline type fuels. The data in Table II show that even though this material is recognized to be an effective anti-icing additive in gasoline, it is insufficiently effective in jet fuel to be of any value for this purpose, since it resulted in a pumpability temperature of only 23 F. when added in an amount of 0.1% by wt. to the jet fuel with 2 ml./gal. excess water.

This result clearly demonstrates that materials which are effective anti-icing additives in gasoline are not necessarily effective in jet fuel.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In the method of operating a jet engine which encounters sub-freezing temperatures as low as 76 B, said engine being equipped with a fuel supply system wherein the fuel lines and fuel filter are subject to plugging by ice formed at said sub-freezing temperatures due to the presence of water in the fuel, the step of passing through said fuel system to a combustion zone of said engine, a liquid jet fuel containing a polyethoxylated propylene diamine in an amount sufficient to prevent the formation of ice crystals in said fuel lines and filter from water introduced into said engine with said fuel, said fuel boiling in a range of from about F. to about 600 F., said polyethoxylated propylene diamine being present in an amount of from 0.02 to 0.35 percent by weight and having the formula H(CHzCHzO)Z oHlomm H wherein R represents an alkyl radical derived from a fatty acid and having from 10 to 30 carbon atoms and wherein the sum of the subscripts x, y and z designating moles of ethylene oxide is at least two and not greater than ten.

2. A method in accordance with claim 1 wherein said alkyl radical is derived from a fatty acid selected from the group consisting of coconut oil fatty acids, soya bean oil fatty acids and tallow oil fatty acids.

3. A method in accordance with claim 1 wherein said alkyl radical is derived from tallow oil fatty acids and the sum of said subscripts x, y and z is three.

4. A method in accordance with claim 1 wherein said alkyl radical is derived from coconut oil fatty acids and the sum of said subscripts x, y and z is two.

References Cited UNITED STATES PATENTS DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner 

